I have developed my interest in autoimmunity and signal transduction mechanism in rheumatic diseases both through my interest in basic science and my experience in disease oriented research. My immediate interest is in inhibition of signal transduction mechanism operative in activated cells, which are involved in disease progression. The proposed project will enhance my research skills and will apply state of the art techniques and approaches toward understanding the role of cytokine mediated signal transduction mechanism involved in the disease process. This experience will enable me to attain my long-term goal of becoming an independent investigator. Dr. Ivashkiv's laboratory has expertise in the majority of the techniques needed and has made significant contribution in the understanding of cytokine mediated signaling and its role in disease processes. The scientific environment of the Hospital for Special Surgery and the Cornell University Medical Center provides direct access to an excellent multi-institutional immunology-molecular biology program. The overall goal of this proposal is to understand how tyrosine phosphatase SHP-2, known as a positive regulator of growth and differentiation, can act as an inhibitor of IL-6 mediated signaling. Also, why activation of MAP kinases is essential for inhibition. To address these, our specific aims are: 1) to characterize the role of SHP-2 in inhibition of SF or IL-6 mediated JAK/STAT signaling; 2) to determine whether MAP kinases can modify SHP-2 and 3) to understand the role of SHP-2 as an adapter protein for inhibitory molecules. Aim number 1 will involve phosphatase assays and use of dominant negative mutants of SHP-2 to determine its role in inhibition. Aim number 2 will use mutant constructs of SHP-2 with mutation at the putative MAP kinase sites and serine/threonine phosphorylation assays to determine its modification status by MAP kinases. Aim number 3 will use yeast hybrid systems to characterize the adapter role of SHP-2. These experiments will yield information about how activation of monocytes in the joints, a known cause for pathogenesis, can be inhibited. A greater understanding of the JAK/STAT inhibition process will identify therapeutically relevant targets, important for the cure and management of arthritis.